U.S. patent application number 11/815302 was filed with the patent office on 2008-12-18 for atmospheric-pressure plasma jet.
This patent application is currently assigned to Vlaamse Instelling Voor Technologisch Onderzoek N.V. VITO). Invention is credited to Jan Jozef Cools, Danny Havermans, Robby Jozef Martin Rego.
Application Number | 20080308535 11/815302 |
Document ID | / |
Family ID | 34943252 |
Filed Date | 2008-12-18 |
United States Patent
Application |
20080308535 |
Kind Code |
A1 |
Rego; Robby Jozef Martin ;
et al. |
December 18, 2008 |
Atmospheric-Pressure Plasma Jet
Abstract
A plasma jet apparatus for performing plasma processing of an
article includes: an elongated central electrode (2,15), an
elongated cylindrical outer electrode (1) or two outer electrodes
(15,16) surrounding the central electrode and being coaxial with
the central electrode, or two electrodes substantially parallel to
the central electrode. an electrical insulator (3) or insulators
(18,19) are disposed between the outer electrode(s) and the central
electrode, wherein a discharge lumen having a distal end and a
proximal end is defined between the central electrode and the
electrical insulator(s). A supply opening (6) is disposed at the
distal end of the discharge lumen for supplying a plasma producing
gas to the discharge lumen, A power source (9) provides a voltage
between the central electrode and said outer electrode. The
electrical insulator has a radial or outward extension (40,20) at
the proximal end beyond the outer surface of the outer
electrode(s).
Inventors: |
Rego; Robby Jozef Martin;
(Geel, BE) ; Havermans; Danny; (Beerse, BE)
; Cools; Jan Jozef; (Balen, BE) |
Correspondence
Address: |
MERCHANT & GOULD PC
P.O. BOX 2903
MINNEAPOLIS
MN
55402-0903
US
|
Assignee: |
Vlaamse Instelling Voor
Technologisch Onderzoek N.V. VITO)
Mol
BE
|
Family ID: |
34943252 |
Appl. No.: |
11/815302 |
Filed: |
February 6, 2006 |
PCT Filed: |
February 6, 2006 |
PCT NO: |
PCT/BE06/00008 |
371 Date: |
April 7, 2008 |
Current U.S.
Class: |
219/121.52 ;
219/121.5 |
Current CPC
Class: |
H05H 2001/245 20130101;
H05H 1/2406 20130101; H05H 2001/2412 20130101 |
Class at
Publication: |
219/121.52 ;
219/121.5 |
International
Class: |
H05H 1/34 20060101
H05H001/34 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 4, 2005 |
EP |
05447010.4 |
Claims
1. A plasma jet apparatus for performing plasma processing of an
article, comprising: an elongated central electrode, an elongated
cylindrical outer electrode surrounding said central electrode and
being coaxial with said central electrode, an electrical insulator
coaxially disposed between said outer electrode and said central
electrode, wherein a discharge lumen having a distal end and a
proximal end is defined between said central electrode and said
electrical insulator, a supply opening disposed at said distal end
of said discharge lumen for supplying a plasma producing gas to
said discharge lumen, a power source for providing a voltage
between said central electrode and said outer electrode, wherein
said electrical insulator extends in a radially placed ring at said
proximal end beyond the outer surface of said outer electrode.
2. The plasma jet apparatus according to claim 1, wherein the
electrical insulator further extends towards the distal end at the
outer surface of the outer electrode.
3. The plasma jet apparatus according to claim 1, wherein the
distance between an outer surface of the central electrode and the
inner surface of the electrical insulator lies between 0.1 and 10
mm.
4. The plasma jet apparatus according to claim 1, wherein the power
source is arranged to provide an AC or Pulse DC voltage between 1
and 10 kV.
5. The plasma jet apparatus according to claim 1, wherein said
electrodes are tubular.
6. The plasma jet apparatus according to claim 1, wherein said
outer electrode comprises a front and backside which are
substantially parallel to the central electrode.
7. The apparatus according to claim 6, wherein said central
electrode comprises a round extension at the proximal end, along
the entire length of the central electrode.
8. The plasma jet apparatus according to claim 1, further
comprising a supply canal through the central electrode, for
introducing reactive chemical compounds immediately into plasma
afterglow at the proximal end.
9. A plasma jet apparatus for performing plasma processing of an
article, comprising a central electrode, at least two outer
electrodes at both sides of said central electrode and being
substantially parallel to said central electrode, at least two
electrical insulators disposed substantially parallel between said
outer electrodes and said central electrode wherein a discharge
lumen having a distal end and a proximal end is defined between
said central electrode and said electrical insulators, a supply
opening disposed at the distal end of said discharge lumen, for
supplying a plasma producing gas to said discharge lumen, a power
source for providing a voltage between the central and the outer
electrodes, wherein said electrical insulators extend outwardly at
the proximal end beyond the outer surface of the outer
electrode.
10. The apparatus according to claim 9, wherein the electrical
insulators further extend towards the distal end at the outer
surface of the outer electrodes.
11. The apparatus according to claim 9, further comprising a supply
canal through the central electrode for introducing reactive
compounds immediately into plasma afterglow at the proximal
end.
12. The apparatus according to claim 9, wherein the central
electrode is a flat electrode.
13. The apparatus according to claim 9, wherein said central
electrode comprises a round extension at the proximal end, along
the entire length of the central electrode.
14. A method for producing a plasma flow, comprising the steps of:
providing a plasma jet apparatus for performing plasma processing
of an article, comprising: an elongated central electrode, an
elongated cylindrical outer electrode surrounding said central
electrode and being coaxial with said central electrode, an
electrical insulator coaxially disposed between said outer
electrode and said central electrode wherein a discharge lumen
having a distal end and a proximal end is defined between said
central electrode and said electrical insulator, a supply opening
disposed at said distal end of said discharge lumen for supplying a
plasma producing gas to said discharge lumen, a power source for
providing a voltage between said central electrode and said outer
electrode and wherein said electrical insulator extends in a
radially placed ring at said proximal end beyond the outer surface
of said outer electrode; providing a plasma gas flow through the
supply opening; providing a reactive chemical compound (e.g.
monomer) flow through the supply opening and/or through the central
electrode introducing the reactive chemical compound in the plasma
discharge at the open end of the plasma; and providing a voltage
between 1 and 100 kV between the central electrode and the outer
electrode.
15. A method for producing a plasma flow, comprising the steps of:
providing a plasma jet apparatus for performing plasma processing
of an article, comprising: a central electrode, two outer
electrodes at both sides of said central electrode and being
substantially parallel to said central electrode, two electrical
insulators disposed substantially parallel between said outer
electrodes and said central electrode wherein a discharge lumen
having a distal end and a proximal end is defined between said
central electrode and said electrical insulators, a supply opening
disposed at the distal end of said discharge lumen, for supplying a
plasma producing gas to said discharge lumen, a power source for
providing a voltage between the central and the outer electrodes,
wherein said electrical insulators extend outwardly at the proximal
end beyond the outer surface of the outer electrode; providing a
plasma gas flow through the supply opening; providing a reactive
chemical compound (e.g. monomer) flow through the supply opening
and/or through the central electrode introducing the reactive
chemical compound in the plasma discharge at the open end of the
plasma; and providing a voltage between 1 and 100 kV between the
central electrode and the outer electrode.
Description
FIELD OF THE INVENTION
[0001] The present invention is related to a plasma processing
apparatus usable for plasma cleaning, surface modification and
surface coating. More in particular, the present application is
related to a novel plasma jet.
STATE OF THE ART
[0002] Atmospheric-pressure plasma jets are known in the art, e.g.
as described by WO 98/35379 or WO 99/20809. These plasma jet
devices comprise two coaxially placed electrodes defining a plasma
discharge space between the outer diameter of the centrally placed
electrode and the inner diameter of the outer electrode. A plasma
jet can be generated at an open end of the device by introducing a
flow of gas at a closed end of the device while a sufficient
voltage is applied between the electrodes. Between said electrodes,
a dielectric material can be placed to avoid arcing. The jet of
plasma can be used to etch, clean or coat a surface. In the prior
art devices, it is difficult to obtain a reasonably efficient
plasma jet, due to several constraints of the currently known
devices. For example, it is currently impossible to activate rubber
sufficiently with a reasonably sized state-of-the-art classical
plasma jet due to insufficient energy output. Most plasma jet
devices therefore use nozzles to converge the plasma jet in order
to obtain higher plasma densities. This however has the
disadvantage that the treated spot is smaller and more devices,
more time, or larger devices are necessary to treat a specific
surface.
AIMS OF THE INVENTION
[0003] The present invention aims to provide a more efficient
plasma jet device than known from the state of the art.
SUMMARY OF THE INVENTION
[0004] The present invention concerns an atmospheric-pressure
plasma jet comprising a cylindrical 2-electrode device or a
parallel 3-electrode device. The 2-electrode device can be a
tubular device comprising a central cylindrical metal electrode and
an outer cylindrical metal electrode, said cylindrical metal
electrodes being coaxial and defining a plasma discharge lumen,
said device having an open (proximal) end and a closed (distal)
end, said plasma discharge lumen being open to the atmosphere at
said open end and comprising a gas flow feed opening at said closed
end, a dielectric material interposed between said central
cylindrical metal electrode and said outer cylindrical metal
electrode and is characterised in that said dielectric barrier is
radially extended at said open end.
[0005] One embodiment of the parallel device comprises a central
flat or specially formed metal electrode and 2 outer metal
electrodes, said electrodes being substantially parallel, i.e. at a
constant (.+-.1 mm) distance and defining a plasma discharge lumen,
said parallel device having an open (proximal) end and a closed
(distal) end, said plasma discharge lumen being open to the
atmosphere at said open end and comprising a gas flow feed opening
at said closed end, a dielectric material interposed between said
central metal electrode and said outer metal electrodes and is
characterised in that said dielectric barrier is outwardly extended
at said open end. According to a specific embodiment, the outer
electrodes are connected at the sides to form one electrode which
is coaxial with the central electrode. This embodiment and the
tubular embodiment are therefore two variations of the cylindrical
device with one inner and one outer electrode.
[0006] The present invention concerns thus a plasma jet apparatus
for performing plasma processing of an article. A cylindrical
2-electrode configuration and a parallel 3-electrode configuration
are described. The cylindrical plasma jet device comprises: [0007]
An elongated central electrode, [0008] An elongated cylindrical
outer electrode surrounding said central electrode and being
coaxial with said central electrode, [0009] An electrical insulator
coaxially disposed between said outer electrode and said central
electrode, wherein a discharge lumen having a distal end and a
proximal end is defined between said central electrode and said
electrical insulator, [0010] A supply opening disposed at said
distal end of said discharge lumen for supplying a plasma producing
gas to said discharge lumen [0011] A power source for providing a
voltage between said central electrode and said outer electrode
wherein said electrical insulator extends in a radially placed ring
at said proximal end beyond the outer surface of said outer
electrode. The electrodes can be tubular and coaxial with a
circular cross-section or the central electrode may be a flat,
plate-shaped electrode, while the outer electrode has a front and a
back side which are substantially parallel to the central
electrode. In stead of a flat electrode, the parallel device may
have a central electrode with--at the proximal end--a round
extension along the length of the electrode, while the outer
electrode's front and back faces remain parallel to said central
electrode.
[0012] According to a preferred embodiment, a supply canal is
present through the central electrode for introducing reactive
chemical compounds immediately into the plasma afterglow at the
proximal end.
[0013] The 3-electrode parallel plasma jet device according to the
invention comprises: [0014] A central electrode, for example a
flat, plate-shaped electrode, [0015] 2 outer electrodes at both
sides of said central electrode and being substantially parallel to
said central electrode, [0016] 2 electrical insulators disposed
substantially parallel between said outer electrodes and said
central electrode wherein a discharge lumen having a distal end and
a proximal end is defined between said central electrode and said
electrical insulators, [0017] a supply opening disposed at the
distal end of said discharge lumen, for supplying a plasma
producing gas to said discharge lumen, [0018] preferably, a supply
canal through the central electrode for introducing reactive
compounds immediately into the plasma afterglow at the proximal
end, [0019] a power source for providing a voltage between the
central and the outer electrodes wherein said electrical insulators
extend outwardly at the proximal end beyond the outer surface of
the outer electrode
[0020] In the plasma jet apparatus according to the present
invention the electrical insulator preferably further extends
towards the distal end at the outer surface of the outer electrode.
Advantageously, the distance between an outer surface of the
central electrode and the inner surface of the electrical insulator
lies between 0.1 and 10 mm. The power source is preferably arranged
to provide an AC or Pulse DC voltage between 1 and 10 kV for the
tubular configuration and between 1 and 100 kV for the parallel
configuration.
[0021] Another aspect of the present invention concerns a method
for producing a plasma flow, comprising the steps of: [0022]
Providing a plasma jet apparatus according to the present
invention, [0023] Providing a plasma gas flow through the supply
opening, [0024] Providing a reactive chemical compound (e.g.
monomer) flow through the supply opening and/or through the central
electrode introducing the reactive chemical compound in the plasma
discharge at the open end of the plasma), and [0025] Providing a
voltage between 1 and 100 kV between the central electrode and the
outer electrode.
SHORT DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 represents a prior art plasma jet design.
[0027] FIG. 2 represents a schematic overview of the plasma jet
device according to the present invention.
[0028] FIG. 3 represents a schematic overview of the parallel
plasma jet device according to the present invention.
[0029] FIG. 4 represents a schematic overview of a special
configuration of the embodiment with parallel electrodes.
[0030] FIG. 5 represents a number of possible cross-sections of
parallel plasma jet devices according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0031] State-of-the-art plasma jets, such as depicted in FIG. 1
usually comprise an outer electrode 11 and inner electrode 12, and
a dielectric material 13 interposed there between.
[0032] The tubular embodiment of the present invention can be seen
in FIG. 2 and concerns an atmospheric-pressure plasma jet with 2
coaxial, cylindrical electrodes (1, 2) and with one specifically
formed electrical insulator in the form of a dielectric material 3.
The dielectric barrier is extended at the proximal end of the
plasma jet, preferably in the form of a U-shape extension 20. A
plasma jet operates at temperatures between 30.degree. C. and
600.degree. C. and can be used for plasma cleaning, surface
modification and surface coating. The U-shape dielectric material
has major advantages for all these applications. A ring, so just a
radial extension for the tubular configuration is also a preferable
embodiment (without the return leg 21 of the `U`). At the distal
end of the device, is the supply opening 6, to supply plasma gas to
the lumen defined between the central electrode and the dielectric
material 3. Preferably, the central electrode 2 is connected to
ground 8, while the outer electrode is connected to a voltage
source 9. Electrode 1 connected to the ground and electrode 2
connected to a voltage source is also a possible embodiment. The
embodiment where both electrodes are connected to a voltage source
is also included in this invention. A supply canal 7 through the
central electrode 2 can be present for introducing reactive
compounds immediately into the plasma afterflow at the open end.
The distance 4 between an outer surface of the central electrode
and the inner surface of the electrical insulator lies between 0.1
and 10 mm. The distance 5 is the diameter of the homogenous plasma
zone. The distance 50 is the height of said homogenous plasma zone,
corresponding to the height of the external electrode 1.
[0033] The central electrode 2 and the outer electrode 1 can be
cylindrical with a circular cross-section, i.e. tubular.
Alternatively, the central electrode may be a flat electrode 2,
while the outer electrode 1 comprises a front and backside 70, 71
(see FIG. 5A), connected at the sides 72 to form one cylindrical
outer electrode 1. The insulator 3 then also comprises front and
backsides 73,74 parallel to the central electrode, and connected 75
at the sides to form one cylindrical insulator 3.
[0034] FIG. 3 shows the plasma jet device according to the
invention, equipped with 3 parallel electrodes. The device
comprises a central electrode 15, and two parallel electrodes 16,
17 on either side of the central electrode. The figure shows a
cut-through view of the device. The actual device is of course
closed on the sides. Possible cross-sections are shown in FIG. 5B
to 5D. The devices shown in FIG. 5B to 5D are closed at the sides
by suitable insulating materials (not shown). The parallel device
of FIG. 3 has two dielectric portions 18, 19 which are
substantially parallel to the electrodes. At the distal end of the
device, the supply opening 6 is present to supply a plasma
producing gas to the discharge lumen defined between the central
electrode and the insulators. A supply canal 7 through the central
electrode 15 can be present for introducing reactive compounds
immediately into the plasma afterflow at the open end. The central
electrode 15 is connected to ground 8, while the outer electrodes
16,17 are connected to a voltage source 9. The embodiment where the
outer electrodes 16, 17 are connected to ground and the central
electrode 15 is connected to a voltage source is also included in
this invention. Also, the embodiment where both the central
electrode 15 as the outer electrodes 16, 17 are connected to a
voltage source are included in this invention. At the proximal end
of the device, the dielectric portions are produced with an outward
extension 40, preferably in the shape of a U, or with a flat
outward extension, so without the returning leg 41 of the `U`. The
distance 4 between an outer surface of the central electrode and
the inner surface of the electrical insulator lies between 0.1 and
10 mm. The distance 5 is the width of the homogenous plasma zone.
The distance 60 is the height of said homogenous plasma zone,
corresponding to the height of the external electrodes. The
distance 61 is the length of the plasma zone, corresponding to the
length (depth) of the device.
[0035] FIG. 4 shows a possible special configuration of the
parallel plasma jet device according to the invention. In this
configuration, there is a round extension 30 along the entire
length of the central metal electrode 15 at the said open end of
the plasma jet. As shown in FIG. 4 both the specifically formed
dielectric material (18,19) and the outer metal electrodes (16,17)
have a special form in order to guarantee a constant (.+-.1 mm)
distance between the outer surface of the central electrode and the
inner surface of the electrical insulator. Reference 60 shows the
height of the plasma jet, 5 the broadness of the homogenous
effective plasma afterglow and 61 the length of the plasma zone in
between the parallel electrodes. Because of the round extension 30,
the concentration of the afterglow and thus the plasma density in
the afterglow are increased.
[0036] In general, the following operating characteristics can be
used when using the plasma jet according to the present invention:
[0037] Electric power for the tubular device with an electrode
height 50 of 10 cm (from here called tubular device): 20-750 Watt;
[0038] electric power for the parallel device (including parallel
device with one outer electrode) with an electrode height (50,60)
of 10 cm and an electrode length (61) of 10 cm (from here called
parallel device): 100-5000 Watt. Applied power is dependent upon
application. [0039] Electric voltage (8): 1-100 kV [0040] Plasma
gas flow (6): 1-400 l/min for the tubular device, 10-4000 l/min for
the parallel device. [0041] Temperature preheated plasma gas:
20-400.degree. C. (This means the plasma gas can be preheated up to
400.degree. C. before being inserted in the plasma jet). [0042]
Plasma gases: N.sub.2, Air, He, Ar, CO.sub.2+mixture of these gases
with H.sub.2, O.sub.2, SF.sub.6, CF.sub.4, saturated and
unsaturated hydrocarbon gases, fluorinated hydrocarbon gases.
[0043] Monomer flow: 1-2000 g/min (through canal 7 in the central
electrode immediately into plasma afterglow). [0044] Feed gas flow:
0.1-30 l/min (through canal 7 in the central electrode immediately
into plasma afterglow). [0045] Inner gap distance (4): 0.1-10 mm
(dependent upon plasma gas and application). [0046] Diameter (for
tubular device) or broadness (5) (for parallel device) of the
homogeneous plasma zone: 6-80 mm. [0047] Length of effective plasma
afterglow: 5-100 mm. (dependent upon application).
[0048] When a high voltage AC or pulsed DC power is put on one of
the electrodes, a dielectric barrier discharge takes place in
between the dielectricum and the inner electrode. The active
species from the plasma are blown out of the plasma jet by the
plasma gas flow. This afterglow is directed against a sample and
this way 3-D objects can be plasma treated. In case a pulsed DC
power is used, the frequency is preferably comprised between 1 and
200 kHz, and advantageously between 50 and 100 kHz
[0049] The advantages of the radially or outwardly extending
dielectricum from the plasma jet apparatus according to the present
invention can be summarised with the following 3 concepts: distance
to the plasma source, width of activation and consumption of plasma
gases.
Distance to the Plasma Source
[0050] It should be noted that radicals, and particularly ions, in
the plasma discharge are extremely short lived, and can almost not
be transported outside the discharge region. Metastable species
produced inside the plasma, on the other hand, have longer
lifetimes at atmospheric pressure, typically in the order of
hundreds of milliseconds. This longer lifetime allows them to be
carried out of the plasma volume with the plasma gas flow.
Obviously the most reactive metastable species will be lost first.
The closer to the plasma source the more reactive the plasma
afterglow. With the novel plasma jet apparatus according to the
present invention, samples can be brought up to 2 mm from the
actual plasma source. Experiments have shown that stable activation
of certain polymers can only be realised when using the described
plasma jet configuration with the radially or outwardly extending
dielectricum.
EXAMPLES
Plasma Activation of Rubber
[0051] Rubber is impossible to activate sufficiently with the
classical concept: the distance rubber/plasma source seems to be
too large. The most reactive and in this case needed species of the
plasma are lost before they hit the rubber sample.
[0052] When using a U-shaped dielectricum such as in FIG. 2, more
reactive plasma afterglow is obtained Parameters: [0053] Power: 400
Watt [0054] Frequency: 70 kHz [0055] Plasma gas: 65 l air/min
[0056] Precursor: none [0057] Temperature plasma after glow:
65.degree. C. [0058] distance rubber/plasma source: 4 mm [0059]
surface energy before plasma activation: .+-.20 dynes. [0060]
surface energy after plasma activation: >75 dynes. [0061]
surface energy 1 week after plasma activation: 62 dynes.
Plasma Activation of PVC:
[0062] PVC is thermal sensitive. The activation performed with the
classical concept is not stable in time. After a few hours,
activation was completely lost.
[0063] When using a U-shaped dielectricum, more reactive plasma
afterglow is obtained. [0064] Power: 300 Watt [0065] Frequency: 32
kHz [0066] Plasma gas: 60 l N.sub.2/min. [0067] precursor: none.
[0068] Temperature plasma afterglow: 60.degree. C. [0069] distance
PVC/plasma source: 5-7 mm. [0070] surface energy before plasma
activation: 45 dynes. [0071] surface energy after plasma
activation: >75 dynes. [0072] surface energy 1 week after plasma
activation: 64 dynes. [0073] surface energy 1 month after plasma
activation: 56 dynes. [0074] surface energy 4 months after plasma
activation: 54 dynes.
Width of Activation
[0075] If flat samples are brought close to a plasma afterglow, the
active species of the plasma afterglow are spread out over a
certain region in between the plasma jet and the samples. This
means that the activated spot can be much broader than the diameter
of the plasma jet. The closer the samples are brought to the actual
plasma source, the broader the activated spot will be. Experiments
have confirmed that with the plasma jet according to the invention
(with U-shaped dielectricum) this activated spot for the same
plasma conditions is much broader than with the classical
concept.
EXAMPLES
Plasma Activation of Polyethylene
[0076] Increasing the broadness of the activated spot would
decrease the overall working costs of a (multi-) plasma jet. When
using a plasma jet according to the present invention, more
reactive plasma afterglow is obtained and active species are spread
out over a broader region. [0077] Power: 200 Watt [0078] Frequency:
50 kHz [0079] Plasma gas: 50 l N.sub.2/min [0080] Precursor: none
[0081] Temperature plasma after glow: 65.degree. C. [0082] diameter
plasma jet: 15 mm [0083] surface energy before plasma activation:
32 dynes. [0084] surface energy after plasma activation: 62
dynes.
TABLE-US-00001 [0084] Distance sample/plasma Broadness of
homogenous source (mm): activated spot (mm) (62 dynes): 2.5 45 4 41
6 25 8 22 10 22 12.5 22 15 22 20 18 30 7 35 3
[0085] With the classical concept the broadness of homogenous
activated spot was maximum 32 mm at 1.5 mm distance sample/plasma
jet.
Plasma Activation of Polypropylene
[0086] Increasing the broadness of the activated spot would
decrease the overall working costs of a (multi-) plasma jet. When
using a plasma jet according to the present invention, more
reactive plasma afterglow is obtained and active species are spread
out over a broader region. [0087] Power: 200 Watt [0088] Frequency:
50 kHz [0089] Plasma gas: 50 l air/min [0090] Precursor: none
[0091] Temperature plasma after glow: 65.degree. C. [0092] diameter
plasma jet: 15 mm [0093] surface energy before plasma activation:
36 dynes. [0094] surface energy after plasma activation: 70
dynes.
TABLE-US-00002 [0094] Distance sample/plasma Broadness of
homogenous activated source (mm): spot (mm) (70 dynes): 2.5 48 4 45
6 26 8 22 10 22 12.5 22 15 22 20 20 30 12 35 4
[0095] With the classical concept the broadness of homogenous
activated spot was maximum 33 mm at 1.5 mm distance sample/plasma
jet.
Consumption of Plasma Gases/Plasma Power
[0096] As a consequence of the fact that the samples can be brought
closer to the actual plasma zone, less reactive species are lost in
the afterglow. So compared to the classical plasma jet, the same
effect can be obtained with a lower consumption of gas and/or
power. This last advantage can be seen as an indirect consequence
of the two former advantages.
[0097] It has been shown experimentally that one needs less gasses
and/or power for the same plasma activation effect. Such
experiments can be performed by the skilled person.
* * * * *